Pressure and temperature relief valve



Au 26, 1941'. o, F, CARL O'N 2,253,930

PRESSURE AND TEMPERATURE RELIEF VALVE Filed July 11; 1940 3 Sheets-Sheet 1 dwarf Aug. 26, 1941. o CARLSON 2,253,930

PRESSURE AND TEMPERATURE RELIEF VALVE Filed July 11, 1940 3 Sheets-Sheet 2 All OscarITar9m..

Aug. 26, 1941. OF. CARLSON 2,253,930

PRESSURE AND TEMPERATURE RELIEF VALVE Filed July 11, 1940 3 Sheets-Sheet 3 76 E4 mrors Dm/N BEN/Aw A I x In i/ntor 0564017 Carlson Patented Aug. 26, 1941 UNIT ED STATE I 2,253,930- s PATENT OFFICE PRESSURE ANDTEMPERATURE RELIEF VALVE Oscar F. Carlson, 'Kenilworth, Ill., assignmof one-half to Oscar Carlson Company, Chicago, 111., a corporation of Illinois, and one-half to Everett N. McDonnell, Chicago, 111.

Application July 11, 1940, Serial No. 344,887

11 Claims.

Thisinvention relates generally to relief valves, and more particularly to valves which are pressure and temperature responsive.

The general object of this invention is to provide a quick-acting valve, responsive to predetermined conditions of pressure and temperatures. and which has a positive open and shut snap 'action. Such valves are required upon water heating systems and closed space heating systems to avoid possible damage or injury to which might otherwise be generated in the systemQCauses of excessive pressure in such systems are generally excessive heat input. Thus, for example, assume a domestic hot water heater is being fired to provide a supply of hot water.

If the fire is allowed to continue after the water in the tank has become heated tothe desired temperature it continues the heat input and presently the temperaturewill reach the boiling point for the. pressurev under which the tank is operating and then the-pressure will begin to rise as steam is formed and tends to occupy a part of the closed space.

Such -a condition is dangerous because the pressure might cause an explosion or other damage and the excessive temperature might injure some one.

should'retaln all the fluid pressure below the predetermined excess value. cess pressure is produced by heat input the valve should be opened promptly and itis unsafe to close the valve again unless and until the temperature in the closed system has dropped to a predetermined low value which value will be so property and persons from excessive pressures I A relief valve to have any real value must primarily be reliable and must open at the pressure forwhich it is set. I have made tests of various devices upon the market and find that they are not only unreliable in that they fafl to open at the setting but that they begin to leak when the critical pressure is approached.

Now the problem of providing a reliable and accurate pressure relief valve has been solved in the structure disclosed in mycopending application, Serial No.'248,978, filed January 3, 1939,

now .Patent No. 2,248,807, granted July. 8,1941. An adequate pressure relief valve must not only open when the predetermined pressure has beenattained but it must open wide enough to permit the outflow of'fluid-water and/or steam-- bearing heat, at such a rate that the loss of heat from such outflow is faster than the input of If this be not the case the If the relief valve opens it is primarily because of excessive heat input and therefore it may be assumed that heat is beingaccumulated and the,

only safe thing for the relief valve to do is to blow the pressure down to a safe temperature.

In other words, assumethat a hot water boiler low as to be safe imder all conditions of firing or to indicate that firing has actually been discontinued.

In brief, a pressure relief valve on this service usually opens from pressure due to heat input. The attainment of excessive pressure (as accurately determined by a reliable responsive device) is an indication of a dangerous heat input. Therefore the valve should according to the concept of the present invention open as soon as a dangerous pressure-temperature condition appears and should not be allowed to close upon the usual blow down differential but should be kept open until the temperature has been brought down to a safe value regardless of pressure conditions.

My present invention aims to provide a valve pressure or temperature or from both, and it is not possible in those devices to have an accurate pressure response and retain the valve open until a temperature definitely and substantially-be low the temperature corresponding to pressure I at which the valve should close, has been reached.

According to my invention the valve is made to open accurately and positively, without leakage, dribbling or variation, at a definite value of pressure (as producedby temperature). If the pressure should be due to causes other than excessive temperature the valve opens and blows down the desired differential and then closes, for

there is no need to waste liquid if the cause of opening is pressure only and that pressure has subsided. But according to my invention, if the pressure is due to excessive heatinput, the valve will open precisely at its predetermined setting and release the pressure and then will not close again until the temperature has dropped to a value which shows that a condition has been reached that cannot do injury from either temperature or pressure.

The valve of my invention opens not from temperature alone, but from pressure alone or from pressure due to temperature, and if temperature But when the ex-' firm manner. This is due to the pressure building up to an amount slightly greater than the predetermined setting whereupon the valve member rises, not completely, but only minutely, from the valve seat and frees a small amount of steam. Due to the rate of heat input in the boiler to be controlled, this pressure which raises the valve member slightly is often not great enough to force the valve member fully open, but yet is sufflcient to keep the valve from reclosing. This' intermediate stage in the opening of the valve then permits a constant leakage and dribbling. Another common fault of the present day valves is that in addition to the dribbling there is a tendency to pop. That is, the temperature builds up in excess of the predetermined setting and the valve, which is the ordinary spring-loaded type, is opened; whereupon pressure is released and the valve springs shut. A moment later it pops open, and again quickly pops shut. There is not a sufficient sustained release; this results in a constant popping open and shut.

These faults of dribbling and popping are comman not only to pressure relief valves, but also to temperature relief valves or such valves as are a combined form of temperature and pressure relief valves.

To overcome these dimculties, I provide in this invention biasing means for holding the valve member tightly upon the valve seat by a force greater than the pressure produced within the system and bearing against the valve surface until a critical and predetermined pressure has been reached. At that critical point a portion of the force holding the valve member firmly seated is reversed which causes the valve member to snap away from the valve seat into fully open position.

The valve remains open, then, until the pressure is released and lowered to the predetermined amount, whereupon the force tending to close the valve overcomes the pressure within the system, and the valve member snaps tightly shut upon its seat. Popping and dribbling is done away with.

This snap action is produced by a cam and roller arrangement, the cam being spring loaded and the roller being borne on the valve member stern. Cam and roller arrangements havebeen used before, but in all such cases leakage and dribbling have resulted, since the valve stem bearing the roller has had to rise slightly from its seat before sumcient relative motion between the cam and roller has occurred to talre the roller over the peak of the cam and open the valve fully. With such an arrangement a tightly seated valve was unobtainable. Additions of temperature relief controls to such devices increased the leakage.

In my present invention a snap action is produced by the use of a cam and roller, but the relative motion between the elements of the snap mechanism is produced by movement of a pressure responsive element, such as a spring loaded expansible bellows. The bellows permits the necessary relative travel between the snap memberswithout allowing any relative motion between the valve and its seat. In fact in the preferred form, the expansion of the bellows increases to some degree the loading of the valve member against the valve seat. In the preferred embodiment of my invention, I mount the valve seat upon the.

aasaaso top of the bellows which thereby allows the expansion of the bellows to carry the seat and the valve against the loading spring, while securing the necessary motion of the valve stem which, in turn, carries one element of the snap action. This motion of seat, valve and associated snap element carries that snap element past the crest of the cam of the cooperating element. Thereupon the loading of the snap mechanism, which previously tendedto hold the valve firmly against the seat, now raises the valve suddenly from its seat into fully open position. This action allows no dribbling or leaking. When the pressure is sufficiently released, the spring loading of the seat member which pulls the valve stem and head down with it forces it, and the roller it bears, back past the peak of the cam whereupon the spring loaded cam by its additional force snaps the valve firmly back upon its seat.

With this pressure responsive unit, I provide a temperature-responsive relief control. These two units work in conjunction when pressure due to heat input is increasing too rapidly. Should the situation arise where the valve has been snapped open due to excess pressure, and the pressure has been relieved without a proper or predetermined lowering'of the temperature, then the tempera-' the end of such bellows an arm is borne which,

when moved by expansion of the bellows due to increased heat, shifts the cam and its peak. When the temperature and its corresponding pressure is excessive, the peak of the cam is moved down over the roller while the pressure responsive bellows acts to move the roller up over the peak. This means the cam is not stationary in respect to the movement of the roller, but

. instead moves toward the roller, and thus effects the passage of the roller over the peak. Such passing of the peak of the cam snaps the valve into fully open position.

As the temperature is reduced to its proper and predetermined level, the bellows of the temperature responsive element contracts and the arm it bears forces the cam, with its peak, up and past the roller which is borne on the valve stem. At that moment then, the spring loading of the bellows acting upon the valve stem and head, with this addition of the spring loading on the cam, snaps the valve tightly shut.

Other objects and advantages of the present invention will appear more fully from the following detailed description which, taken in conjunction with the accompanying drawings, will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention.

The preferred form is not the only form in which may be embodied the broad concept of producing relative motion between the elements of the snap mechanism without producing relative motion between the valve and the seat. The

preferred form is advantageous in many ways,

but obviously the invention is not limited to the preferred form.

In the drawings:

through a pressure and temperature relief valve with the parts shown in the position they occupy when the valve is closed;

Figure 2 is a longitudinal section similar to Figure 1, but shows the parts in the position they occupy when the valve is open due to excessive pressure alone;

Figure 3 is the same longitudinal section as shown in Figure 1, but indicates the position of the parts when the valve. remains open due 1 to excw'sive heat after pressure has been released;

Figure'4 is aplan' view with the upper half of the casing, the two springs and the electric switch unit removed;

Figure 5 shows the pressure and temperature relief valve as applied toa heating plant boiler with circulation of the fluid through the pipe outlet as indicated by direction of the arrows;

Figure 6 shows the pressure and temperature relief valve as applied to a hot water supplying unit'and using a T-joint and pipe for circulation of the fluid (circulation indicated-by the arrows) instead of circulation through the optional outlet as built in the valve itself; and

Figure 7 is a fragmentary view of the spring bracket connecting the biasing spring with the shiftable'valve seat holder.

Referring now more particularly to Figures 1 to 4, inclusive, the casing i of the pressure and temperature relief valve includes an upper casing portion, or spring housing, 2 and a lower section, or valve housing, 3. The upper and lower portions of the casing are firmly secured together by screws of the type as indicated at reference numeral 3 and between the housings 2 and 3 there is clamped a guide plate 3, a flexible diaphragm l3 and an arresting plate II for the spring diaphragm i3.

1 A free-floating flexible bellows l2 which is sealed at its lower end to a shoulder I3 as by soldering, around the inlet l4, carries on its upper end a valve seat holder l3. This valve seat holder I3 is cylindrical in form and has a flange H to the under side of which is soldered the upper end of the,flexible bellows i2. The lower and cylindrical portion 13 of the valve seat holder 42 in maintaining the lower end of the spring in 43. 'In order to hold the spring 41 in place on the plate 43, tongues 42 are slit and are bent upwardly from the plate 43 to a distance substantially equal to the diameter of the wire from which the spring 4| is formed. The ends of the arms 31 extend through the plate 43 a similar amount and therefore cooperate with the tongues place.

Therefore it may be seen that the effective force of the compressed spring 4! is transmitted to the valve seat holder I3 through the arms 31 and pan-shaped ring 33 and tends to resist movement of the flexible bellows I2 when it is subiected to pressure on its interior.

The upper portion'of the spring bears against the plate 43 which in turn flts against the washer 44. The plate 43 has'a downwardly extending terior of the bellows I2 tending to raise it and A When the cap 41 is removed a socket wrench may be inserted into the socket '43 in the head of the adjusting screw 43 which is resting in a suitable recess 33 in the housing 2. g V I The gas or liquid under pressure flowing into this unit through the inlet 3| enters an opening i4 and thence passes into the interior of the flexible bellows and the passageway 53 of the valve seat 23. The pressure acts against the in-' acts upon the face of the-valve member 34 trying to raise it also. The valve member 34 has a shank 33 which is firmly set in the'valve stem 31. The valve stem 31 slides on transverse ribs 33 in thecylindrical guide 33 which is screwed into liquid, which is under pressure, from the flexible bellows to the outlet 2| of the valve when the valve opens. The upper cylindrical portion 23 of the valve seat holder i3 has ports 21 through which pressure and vapor is released tothe outlet 23 at the rear of the assembly when the valve is open. The uppermost portion of this valve seat holder l3 carries a flange 33 which bears tightly against the diaphragm l3 and a washer 3i pressing them against the shoulder 32 and the pan-shaped ring 33 which encircles and bears against the shoulder 34 of the cylindrical guide 33.

This pan-shaped ring has upwardly-extending and separated arms 31 (see Figure '1) which extend from the ring 33 in the lower half of the casing I up through the guide plate 3 intothe upper half of the casing. The upper portion of the arms 31 are reduced, as at 33, and are inserted into suitably formed slots in a plate 43 serving as a base for a biasing spring 4|, the lower end of the latter seating againstthe plate ,carried by the U-shaped, bracket '33. Thisthe upper portion of the valve seat holder l3.

This cylindrical guide 33 has, intermediate its ends, a flange whose shoulders 32 and 34"firmly clamps the ring 33, the washer 3|v and the spring diaphragm i3 firmly against the flange 33 of the valve seat holder 13. I

v The upper portion of the valve stem 31 is split into two arms 33 which carry the pin 33 of the sleeve 31 which is borne between the arms 33 on said pin. This sleeve 3| and pin 33 passes through the rockerarm 32 at the elongated slot 33. This rocker arni 32 consists of two bars 12 and 13 (Figure 4) and at the left end the rocker arm 32 is pivoted at 33 about a pin 34 which is carried by the two upright supports which are indicated each in their entirety by the reference numerals 33 and 31 (Figure 4). These supports each have a flange 13 and 1! which are riveted as at 39to the guide plate 3. I

The right hand ends of the bars 12 and '13 are offset and carry a cam roller 13 disposed between them (Figure 1). v

A bellci'ank detent member 1a in the form of a cam bears againstthe cam roller 13 and in its apex is pivoted on the pin 30, which is carried by the two supports 33 and 31,:and its horizontal arm is pivoted on the pin 32 which is U-shaped bracket as is fastened to the cup '04 by the reduced 'end of the rod 33 being'passed through the elements 33 and 34 and being peaned over as at 31. The rod 33 extends into the inupper portion of the spring roller ll.

The compression of the its force by leverage on the cam member I9 through the pivot pin 82 and the arm 95 thus tending to swing the lower end "of the cam member 19 in an arc downward and to the. right about pivot pin 89 as a center. Such pivoting of the lower end 82 of the cam member 19 is resisted by the cam roller 19, borne between the two end portions of the rocker arm 92. The compression of the spring 99, then, as may be seen, ultimately transmits its force to the valve thepin 80 which is fastened through the upper end 59 of the valve stem 51.

Such force against the cam roller 18 is transmitted to the rocker arm 92 which carries the The rocker arm is therefore pushed downward, about the pin 84 as a center, and acts through the pin 60 against the valve stem 5'! since the arms 59 of the valve stem 51 carry the pin 60. As may be seen then, the compressed spring 89 ultimately exerts its force on the valve stem 51 and seats the valve head 54 tightly against the valve seat 23.

Though this valve is a combination pressure and temperature relief valve it will open from pressure alone with the same positive snap action.

The snap action of the valve can most easily be explained by a description of the action of pressure alone on the --.valve, 1. e., exclusive of temperature, so I shall first describe such action and 'will follow with a description of the snap action as controlled by both pressure and temperature. The pressure'within the system to be controlled acts upon the valve head 54 and the flexible bellows l2. As previously shown, the compressed spring 4! resists the upward expansion of the bellows, and the compressed spring 89 resists upward movement of the valve head 54 away from the valve seat 23. As the pressure increases, the flexible bellows will expand and move upwardly against the resisting spring 4i thus compressing it. The valve will remain tightly closed for its valve seat is borne upwardly along with the-flexible bellows i2 and thus tends to compress the spring 39 even more. As the bellows it carries the valve seat, valve head and valve stem up, the rocker arm is forced upwardly too, about the pivot pin 8%, and this exerts a force through the cam roller it and cam member 79 against the spring til. The cam roller in being forced upwardly along with the rocker arm 82 not only exerts pressure against the side 98 of thecam arm as but also rolls upwardly along the side 86.

S0, prior to a critical and predetermined pres- -sure within the unit the spring 89 will press the valve head El i more and more tightly against the seat 23, until at the predetermined setting the pressure within the unit will have forced the bellows l2, the valve seat 28 and therefore the valve head 56 and stem 5? and rocker arm 82 up to such a point that the cam roller 18 will reach and pass over the peak of the cam to the upper side 9? of the cam arm 92. As the roller 78 passes the peak, it ceases to compress the spring 89 whereupon that spring descends and the cam member 19 swings to the right about the pin 90 and thereby suddenly forces the cam spring 89 then exerts stem 51 through the cam member I9, the cam roller 19, the rocker arm 82 which carries the cam roller 18 and thence to the sleeve'il and the tangs 90 which are struck down from the plate 0.

18 snaps the valve ofl. its seat into fully open position and releases the pressure within the unit. The valve will never stop on dead center because the internal pressure acting on the face of the valve will throw it upwardly away from its seat as soon as the holding force of the detent is lost. Prior to such snap opening there has been no leakage or dribbling as in other valves.

Any gas or liquid that is released passes through the valve throat 59 (see Figure 2) and out'its opening 2|, then through the ports 21 of the 4 lower opening of the valve stem guide 39 and roller 16 up along the cam surface 91. This sudprevents any fluid or liquid from passing up through this valve stem guide. This sealing action in conjunction with the diaphragm it completely closes oh the spring housing 2 from the lower half of the unit, the valve housing I.

The lift of the rocker arm 62 by the leverage exerted by the spring 89 on the arm 85 of the cam member 19 (when the valve has snapped open) is such that the valve will be kept open until the pressure has been released to a predetermined point. At that time the force of the spring ll will have overcome the excessive pressure released from within the unit and will collapse the bellows I2, which will-draw the valve seat 23, the valve seat'holder l9 and the valve stem guide 39 down with it. And the valve stem.

guide 36 bearing against the surface 99 of the valve head will cause the valve head 54 and stem 31 to come down and pull the rocker arm 62 with them. The descent of the rocker arm due to the force of the spring 4i will overcome the force of the spring 99 against the cam roller 16 and will cause the roller tolmove along the cam surface 91 to the peak of the cam. When the roller 16 moves toward the peak of the cam it forces the cam member I9 to move toward the left about the pivot pin which compresses the spring 89. This compression of the small spring 89 is not great enough to resist the downward movement of the valve seat holder, valve seat and valve head caused by the larger and stiflfer spring ti.v When the cam roller I6 passes just beyond the peak of the cam member 19, the compression of the spring 89 will be released and the roller 18 will be suddenly forced down along the under side 96 of the cam 79 as this-cam member is swung back to the right by the downward release of the spring 89 which will cause the head 55 to snap tightly shut against the valve seat 23. The snap action is positive and quick and occurs exactly at a predetermined lowering of the pressure, just as the opening of the valve occurs precisely at-the predetermined increase of pressure with the same positive snap action.

The above description of the valves opening and closing by pressure, exclusive of temperature, was for purposes of explaining clearly the snap action of the valve. Such pressure without much heat would be found in a compressed air system or cold water system, for example. But for pressure due to heat a heat control element cooperating with the pressure responsive element is necessary from the point of view of safety, and is the chief object of my invention.

In a system such. as a hot water tank installation (Figure 6) or closed hot water boiler insure-to a low enough amount will not alway ports 33 and 31 also bear the pin 33 which passes through an arm of the cam member 13 and through the ends of the rocker I31; There are slots in the left hand ends of the rocker I31 and in the supports 33 and 31 through which pin 33 passes. but there is no slot in the cam member 13 around this pin.

The upward expansion of the bellows I2I (see Figure 3) forces up the rocker arm I31 causing open it.-until the temperature has been reduced to a predetermined value. By this means all pressure and heat are reduced to such an amount that they can not quickly rise to their former dangerous level. There may also be" provided in this relief unit a cut-out switch which will shut down the heat supplying means or sound an alarm when the valve is opened.

In such a pressure and temperature relief I valve I have provided a bulb III! which contains a liquid expansible under heat. This bulb I I3 is set in an opening H5 in an inner wall I32 of the casing I and projects down into the passageway III so that the heated liquid or gas in flowing through the inlet 3|, passageway III and outlet II2 may surround the container. An inner wall II 1 of thevcasing I helps form the passageway III and separates it from the inlet I4 to the bellows. This bulb III) has a flange II3 that rests against the washer II4, which washer is carried on the shoulder Got the wall I32 of the casing I. To the neck II3 of the bulb III) is sealed an expansible bellows I2I. The top of the bellows I2I carries a threaded extension I22 which passes through the top of the cover I23. This cover I23 fits over the bellows I2I and has a flange I24 on its lower end, and resting on this flange is a spring I23 which spring loads the bellows I2I. The upper end of the spring I23 rests against the internal shoulder I21 of the cylinder or housing I23. This cylinder can'iesa hexagonal flange I30 andextemal threads I3I which are threaded onto the inner wall I32 of the casing I. When this cylinder I23 is screwed into the internal wall I=32 its lower end forces the flange II3 of the bulb IIIlagainst thewasher H4 thereby completely sealing off the passageway III from the upper half (the spring housing 2) of the casing.

Expansion of the bellows, as the heat input increases above the normal amount, forces up the cover I23. Such upward movement of the bellows I2I and cover. I23 is resisted by'the spring I23 which is thereby compressed between the shoulder I21 and the flange I24. This flange I24 serves the additional purpose of guiding the expanding bellows in a vertical plane since the flange I24 flts loosely against the inner wall of the cylinder I23.

To the stud I22 of the bellows I2I is threaded a cylindrical member I34 which has a pin I33 insertedthrough it and also through the arms of the trough-shaped rocker lever I31. The hole in the rocker I31, through which the pin I33 is inserted, is in the form of a slot so that the trough-shaped lever member I31 may pivot fre'ely about the pin I33 when it is raised by the cylinder I34 as the bellows I2I expands. The pin I33'passes through a slot I43 in the middle portion of the rocker lever I31 and is carried. at

"its extremities by the supports 33 and 31. Supit to pivot first about the pin 33 till the slot I43 has been raised to the under side of the pin I33. Atthat time the rocker I31 begins to pivot about pin I33. This forces the left end of the rocker.

I31 to pivot downwardly and slightly to the right carrying the pin 33 and they arm I44 ofthe cam member 13 along with it. The pin 33 passes along in the slot I43 of the supports 33 and 31. This downward movement of the cammember 13 causes the lower side 33 of the'cam to bear.

against and roll down along the cam roller 13. This-downward pressure against the roller 13 keeps the valve head 34 tightly against the valve seat 23. This excess heat input also leads to a rise in pressure which forces up the pressureresponsive bellows I2. As the cam member 13 and its peak are being lowered the expansion of thebellows I2 will push the rocker arm 32 and its cam roller- 13. up and past the peak of the cam.

As soon as the upward movement of the cam roller, due to pressure, and the downward movement of the cam peak due to excessive temperature carry the two elements past each other,

there is a sudden 'uplift of the rocker arm as the roller rides upthe side 31 of the cam member 13 and the valve snaps completely open. opening of the valve allows the excessive pressure (in the form of steam and hot water) to escape. As the steam and hot water escape heat is thereby dissipated, at 4 the same time cold water from the water' supply means enters the tank or boiler and cools down the unit. As shown in Figure 1, there is an electric switch I41 whose control button I43 is snapped by the top of the rocker I31,which has been forced up by the expansion of the bellows I2I. when the control button I43 is thus raised the switch may be adapted to shut off the heat input or sound an alarm or give some other warning. I

When the valve has been opened by this combination of temperature. and pressure, the cam 13 will have been lowered so far that even a complete contraction of the pressure responsive bellows, when the pressure .is fully released, will not allow the roller 13 tom brought down past the cam 13 if there is excessive heat in the system. (See Figure 3). Such excessive heat without accompanying excessive pressure might result, if' the water supply means is clogged or shut down so that no cool water can enter the system after the valve opens. Of course, if the cut-off switch I41 is used (though this relief valve would be safe without it) the heat supply will have been shut 0115, thus stopping heat input and permitting the excessive heat to dissipate moreperature drops and the leverage changes and the cam rises.

' As the excessive heat is liberated and the syscontract and the spring I28 will begin .to collapse the bellows which movement will pull down the right hand side of the rocker arm I31 and thus raise the cam member 19. This will both change the leverage and cause the peak of the cam to rise and pass the cam roller, whereupon the underside 98 of the cam member 19 will bear down on the roller 16 due to the pressure of the spring 89 on the arm 85, and the valve will snap tightly shut, ready for later use. At this time also the electric switch Ill can be adapted to reclose the control circuit of the heat supplying means.

As described above the temperature control element does not act like th present day valves which will open from heat alone and cause dribbling. It is adapted to keep the valve open after the valve has been snapped fully open by a combination of temperature and pressure, but it will not open the valve due to heat alone.

Should the attendant or inspector desire to see whether the valve is operating freelyin its guide or to test the valve for any purpose he need but pull the handle I50 (Figure 1) to the left. This handle is pivoted in the casing, l on a pin lil. As the handle I" is pulled to the left the claw 352 at the opposite end of the handle llll engages-the pin I53, disposed between the separated ends of the bars 12 and 13 (Figures 1 and 4), and causes the rocker arm 82 to pivot about the pin 84 thus raising the valve stem ll in its guide and unseating the valve.

Referring to Figure 1, the turning of the adlusting screw 46 will compress both the larger spring ll and the smaller spring 89 since the washer 44 will be threaded on down the screw 48. Such compression will more heavily load the bellows l2. \At the same time the spring 89 will more tightly force the valve head -54 against the seat 23, though the additional force, due to the compression of the spring 88, will not be as greatly increased as the force due to compression of spring ll since the spring 89 has more turns cylinder I and the rocker Ill. Th rocker, as-

length and small diameter'wire of the spring.

Second, the lowering of the pin 80 due to temperature places the peak of the cam at a different point on the arc of the movement of the roller 18 so that the effective inclination of the upper cam surface is changed, making it more diiiicult for the roller to descend once it is raised. This is apparent because the roller 1 being mounted on the end of the arm. 82 moves in an arc. The roller it normally, when temperature does not cause shifting of the pin 80, lies slightly below horizontal and on passing the crest of the cam' passes slightly above horizontal. Since the distance that the valv ll moves in snapping away fromits seat is always the same, it can be seen that lowering of the pin 80 carries the peak of the cam down. Hence the upper sloping surface ofthe cam is set not so nearly tangent to the arc of movement of the roller but in effect more nearly transverse to the same, producing a greater retarding effect. The retarding effect may be increased by other means.

Under the ordinary situation where excessive temperature and pressure have opened the valve the operator may desire to have the valve remain open until the temperature has lowered even more than it does for the present settingQ That may be accomplished by removing the pin I86 which passes throughthe cylinder I24 and the rocker I 21. with the pin removed, the cylinder I 34 may be turned and threaded upwardly on the threaded extension I22 of the bellows I. The pin I" is then re-inserted through the it has its right end raised by the manual raising of the cylinder I34, pivots about the pin to, for

and a smaller cross-section than spring 4|.

2 Consequently, the valve will not be opened until a greater pressure than before has been built up within the unit to raise the bellows l2 against the spring ll and thus snap open the valve. The compression of the smaller spring 4| increases the differential.

When this increased pressure is formed it will be formed with a corresponding increased temperature. This increased temperature will cause that the roller 18 will not need to rise quite as far as before to snap past the cam, yet such movement of the roller, remember, is not had 2 until the now more heavily loaded bellows l2 rises from the increased pressure within the unit.

It is to be observed that when the thermostat expands to the extent of lowering the pin 80 down in the slot I this has several effects: First, lowering of the pin 80 reduces the compression of the snap action loading spring but this has no substantial effect because of the ,outlet H2 (Figure l).

the pin I39 in the middle of the rocker II! is free to movein the slot I40.

At no time can the manual adjustment result in such a movement of the rocker I31 as to allow the cam member 19 to be lowered enough to open the valve from heat alone. If the operator desires the valve to reclose at a higher temperature than previously, after it has been opened by a combination of temperature and pressure, he need but thread the cylinder down in the opposite direction.

- Figure 5 shows hot water circulation in a heating plant boiler. The outlet 2 (Figure 1) is closed tightly by a plug inasmuch as the outlet H2 is'for optional use in a domestic hot water supplying unit or other small unit where the discharge is not so great as is needed in a heating plant boiler.

Figure 6 shows hot water circulation in a hot supplying unit that is not through the passageway HI and outlet H2 (Figure 1), but is through a T-joint and outlet pipe connected thereto. The relief.unit is screwed into the top of the T-joint and its optional outlet 2 is then closed tightly with a plug. Should circulation through the relief unit itself be desired then the T-joint and its outlet pipe are removed, the plug in the outlet H2 is replaced by the outlet pipe and circulation is through the passageway Ill and While I have shown and described above the preferredstructure in which the principles of the present invention have been embodied, it is to be understood that my invention is not to be limited to the specific details shown and described above, but that, in fact, widely different means may be employed in the practice of the broader aspects ofmy. invention.

1 the other member perature responsive element and having a spring .loading said valve assasso What I claim, therefore, and desire to secure inclined surface for sponsive element being spring loaded to resist the internalpressure to be controlled and having said valve seat fixed thereto, a spring loaded temperature responsive'element subject to the temperature of the fluid to be controlled, a snap mechanism comprising a cam member and a cam-roller member, one of said snap members being carried by saidyalve member and the 1 other of said snap members being carried by valve open until the temperature of the fluid in the casing has been reduced to a predetermined value. a

2. A pressure and temperature relief valve comprising, in combination, a valve seat, a valve seating thereupon, a pressure responsive element subject to the same pressure as the valve, a temperature responsive element subject to the temperature of the fluid acting upon said pressure responsive element, a snap mechanism comprising a cam member and a roller member, one of said members being carried by the valve, and the other member being movable by the temperature responsive element .and having a spring loading which will urge the valve toward or away from its seat in accordance-with the relative position of said cam and-roller members. said pressure responsive element and said temperature responsive element causing relative motion between said cam member and-saidroller member, which motion reverses the action of the spring loading on said valve and snaps it away from its seat when the pressure responsive element and the temperature responsive element are subjected. to that range of predetermined combinations of pressure and temperature at which the valve is set to open.

3. A pressure and temperature relief valve comprising, in combination, a valve seat, a valve said temperature responsive element, said flrst spring actingthrough said snap mechanism to urge the valve toward or away in accordance with the relative position of said cam and roller members, said pressure responsive element and said temperature responsive element causing relative motion between said cam and cam-roller members, which motion reverses the action of the spring loading on said valve and snaps it away from its seat when the pressure responsive element and the temperature responsive element are subjected to that 'range of predetermined combinations of pressure and temperature in which the valve is set to open.

, 6. A pressure and temperature relief valve 1 comprising, in combination, avalve seat, a

Y valve member seating thereupon. a spring means for loading said valve to keep it tightly seated, a pressure responsive element, said pressure responsive element being spring loaded to resist the internal pressure to be controlled and having said valve seat fixed thereto, a spring loaded temperature responsive element subject to the, temperature of thefluid to be controlled, a snap mechanism comprising a cam member and a cam-roller member, one of said snap members I being carried by said valve member and the other seating thereupoma pressure responsive element subject to the same pressure as the valve for moving the valve seat and valve together, a temperature responsive element subject to the temperature of the fluid acting on the pressure element, a snap mechanism comprising a double inclined cam member and a roller member, one of said members being carried by the valve, and

being carried by the temloading which will urge the valve toward or away from its seat in accordance with the relative position of said cam roller members, said pressure responsive element and said temperature responsive element causing relative motion between said cam member and said roller memher, to cause the roller to pass from. one side. of the cam to the other which motion reverses the action of the spring loading on said valve.

4. The combination of claim 2 with means whereby the said temperature responsive element on rise of temperature above a predetermined value changes the position of the cam relative to the roller to keep the said valve fully open when the temperature remains above its lower predetermined setting though the pressure has already been reduced to its lower predetermined setting. a

5. A pressure and temperature relief valve comprising, in combination, a valve seat, a valve member seating thereupon, a spring means for to keep it tightly seated, a

pressure responsive element, said pressure reof said snap members being carried by said temperature responsive element, said first spring acting through said snap mechanism to urge the valve toward or away to snap the valve tightly shut against its seat, when said temperature and pressure are reduced to lower predetermined values.

7. In a temperature and pressure relief valve in combination, a valve seat, a valve member seating thereon, spring means for loading said valve member to keep it tightly seated, a pressure responsive expansible bellows, said bellows carrying the said valve seat and being spring loaded to resist expansion of the bellows due to pressure, a temperature responsive element comprising a bulb and attached bellows, said bulb and bellows being filled with a heat-expansible liquid, a spring for loading said bellows, a snap mechanism comprising a cam member and a cam-roller member, one of said cooperating snap members beingcarried by the valve member and the other being carried by an arm operable by said heat expansible bellows and being loaded by said first named. spring in order to urge the valve toward or away from its seat in accordance with the rela-.

tive position of said cam and roller members,

from its seatfrom its seat in accordance with the relative position of said cam and nail said pressure responsive bellows and said tem perature responsive bellows causing the relative motion between said cam and roller members,

which motion reverses the action of the spring loading on said valve and snaps it away from its seat when the pressure responsive bellowson rise of temperature above a predetermined value changes the effective position of the cam' relative to the roller to keep the said valve fully open when the temperature remains above its predetermined setting though the pressure has already been reduced to its lower predetermined setting.

' 9. A temperature and pressure relief valve comprising, in combination, a casing composed of an upper and lower portion, an inlet in said casing, a valve seat, a valve member seating thereon, a passageway from said inlet, an expansible bellows sealed about the upper end of said passageway and carrying a valve seat holder, said valve seat being disposed within said valve seat holder, aspring reacting between a wall of said casing and said valve seat holder to spring load said expansible bellows, guide means to direct movement of said valvemember and to limit the upward motion of said valve member, a guide plate clamped at its edges between the upper and lower portions of said casing and hav- 1 ing inserted through its center said guide member, a diaphragm clamped around said guide member and clamped at its center between said guide member and said valve seat holder and at its outer edge between said upper and lower portions of said casing in order to seal said upper portion away from said lower portion, a rocker arm pivoted at its center to the upper end of casing from said lower portion, an inlet for said casing and two outlets, one or which outlets permits drainage of the released steam and liquid when the valve opens, the other of which permits circulation through the relief unit of the,

fluid or liquid to be controlled, two passageways from said common inlet, one'oi which leads to the circulatory outlet the other of which leads to the valve structure, a pressure-responsive expansible bellows whose lower end is sealed around the top of said last-mentioned passageway and whose upper end is sealed to a valve seat holder, a valve seat fastened in said valve seat holder, a valve member seated firmly on said seat, a valve member guide for controlling and limiting the movement of said valve toward and away from said valve seat, said valve guide passing through the aforementioned guide plate and clamping a spring bracket and the aforementioned spring diaphragm to said valve seat holder by means 01' a flange on said valve guide, a spring support plate, a spring in the upper portion of said cassaid valve member and pivoted at its fixed end to a support-bracket and having at its free end a cam roller, a detent member, a loading spring therefor weaker than said first mentioned spring, said detent member bearing a cam which is pressed against said cam roller by the compression'of saidlast mentioned Spring. a bulb containing heat expansible fluid subject to the temperature of the fluid acting upon the bellows, a sealed and spring loaded expansible bellows on the upper end of said bulb, said bellows being in the upper portion of said casing and sealed from the lower portion of the casing, an adjustable extension on the upper end of said bellows, a rocker arm pivoted thereto, said rocker arm acting to lower the pivot of the afore-mentioned detent member when the temperature surrounding said bulb increases and causes its bellows to expand, such expansion of the temperature responsive bellows cooperating with theexpansion of the pressure responsive bellows to cause relative motion between said cam member and said cam roller, which motion will snap open the valve when the pressure and corresponding temperature are reached at which the valve is designed to open.

10. A temperature and pressure relief valve comprising, in combination, acasing composed of an upper and a lower portion, saidupper and lower portions being securely fastened together and clamping between them a spring diaphragm and guide plate to seal the upper portion of said ing reacting between a wall of said casing and said expansible bellows by mean of said spring bracket which .is clamped to said valve seat holder on its lower end and extends upwardly through said guide plate to said support plate for said spring in order to spring load said expansible bellows, a lever arm pivoted at its center to said valve member and pivoted at its fixed end to a fixed support and carrying at its free end a cam roller, a bulb and attached bellows loaded with a heat-expansible liquid, said bulb projecting into the aforementioned circulatory passage, said bellows projecting into the upper portion of said casing and being sealed from said circulatory passageway, a spring for loading said heat-expansible bellows and resisting its expansion, a rigid extension on said bellows, said extension having a rocker arm pivoted thereto, said rocker arm being pivoted at its center to a fixed support member and engaging at its inner end a detent member, said detent 'member being spring-loaded and having a cam with a hill which bears against said aforementioned cooperating cam-roller thereby forcing the said lever arm downwardly and the valve member tightly against its seat, a predetermined relative motion of said cam and roller reversing the action of the detent spring to snap the valve open, said relative motion of said cam and roller being produced by expansion of the two Spring-loaded expansible bellows, one acting under pressure and the other acting by reasonoi the temperature of the fluid under pressure. I 1

11. In-a relief valve, a spring loaded valve responsive to excessive fluid pressure to open and relieve said pressure, a spring loaded snap mechanism opposing opening 01' the valve when closed and opposing closing when open, said snap mechanism comprising a hill element and a follower element movable relative to each other for opening and closing said valve with a snap action,

OSCAR F. CARLSON. 

